Krueger Flap and Ultra-High-Bypass-Ratio Through-Flow Nacelle Design for the High-Lift Common Research Model

The design of a vented foldable bullnose Krueger (VFBK) leading-edge flap and an ultra-high bypass ratio (UHBR) through-flow nacelle as an extension of the Common Research Model in High-Lift configuration (CRM-HL) is presented. The modified model is representative of a modern, aerodynamically efficient transport aircraft in landing configuration. The design of the two modifications was performed using Reynolds-averaged Navier–Stokes simulations and was developed within the German Aerospace Center (DLR) project ADaMant. Cross-investigations were made since the VFBK and the UHBR nacelle can also be examined in combination with the original slat and through-flow nacelle of the CRM-HL. In addition, the CRM-HL and its modifications were analyzed in full-scale and as a 5.2% model with the physical environmental conditions of the atmospheric low-speed wind tunnel DNW-NWB (Niedergeschwindigkeits-Windkanal Braunschweig [Low-Speed Wind Tunnel Braunschweig]), where the model will be tested. The VFBK nearly achieves the target of providing a similar lift coefficient at maximum lift at full-scale conditions compared to the CRM-HL with slat. Furthermore, the UHBR nacelle design including pylon and strake achieves a significant improvement by mitigating the separation on the wing and the nacelle, resulting in a similar maximum lift coefficient compared to the CRM-HL with the original nacelle both in full- and in wind tunnel scaling.